Background Emphysema severity on CT predicts five-year functional impairment and reduced survival in the COPDGene study

Aim We ascertain whether mathematical modeling of airway biomechanical properties by maximal expiratory flow/volume curve (MEFV) data could predict five-year emphysema progression as assessed by quantitative CT

Methods We measured the emphysema severity index (ESI), a parameter ranging from 0 to 10, by fitting the MEFV descending limb by an algorithm using as input variables PEF, FEF25, FEF50, FEF75, and FVC absolute values in 4884 subjects of the COPDGene study who had enrollment and 5-year follow-up spirometry and CT data available. ESI is significantly related with emphysema quantitated on CT (Occhipinti, Respir Res 2020) and predicts respiratory mortality in a sample of the Swedish general population (Luoto, Respir Med 2022). We evaluated by principal component analysis (PCA) five-year progression of spirometric data (FEV1,ESI) and co-registered inspiratory-expiratory CT metrics of small airway disease (%fSAD) and emphysema (%pLDA)

Results PCA vectors indicating five-year progression for FEV1 and %fSAD had same direction but opposite versus indicating that FEV1 and %fSAD progression have negative relationship. Airway disease (FEV1,%fSAD) and emphysema (%pLDA) vectors were 90° rotated indicating that five-year progression of airway disease and emphysema are independent. Conversely, ESI vector progression had same direction and versus of %pLDA, suggesting that they are capturing similar information

Conclusions ESI can derive information about five-year emphysema progression comparable to that of %pLDA obtained at CT